But it is doubtful whether inland distances are really comparable with international distances. The cost of maintaining lines of communication between distant countries is often altogether out of proportion to the quantity of mails conveyed; and the sums paid, although ostensibly payments for the conveyance of mails, are often really subsidies, paid sometimes in order to assist the shipping or other industry, sometimes for political purposes.[654] They cannot, therefore, be used as a basis for calculating the amount of postage which should be charged on private letters. This was particularly the case in earlier times.[655] With the expansion of commerce and the establishment for commercial purposes of regular lines of steamers between the principal countries of the world, the task of the Post Office has been much simplified, and, notwithstanding the growth of mails, the cost actually reduced.[656] It is, however, still heavy, and in some cases the payments include an element of subsidy. The cost of transmission by sea of a foreign letter in the British service is on the average 1/4d. Foreign rates are not, however, fixed on a simple cost basis. The reduction to a penny of the letter rate between Great Britain and all parts of the British Empire; between Great Britain, Egypt, and the United States; and between the United States and Germany and France, has been made from considerations of general advantage, political or otherwise, rather than from considerations of immediate profit or loss on the postal service. The international parcel post has always been regarded as primarily commercial,[657] and the service has been deliberately restricted to small parcels on the ground that the conduct of an ordinary transportation undertaking is not a postal function, and that the admission of heavy parcels would render impossible the maintenance of the postal principle of uniformity of rate. Parcel mails are in the international service frequently denied the privilege of rapid transmission accorded to letter mails.[658] The developments of the present war have emphasized the essential distinction to be drawn between communications on the one hand, and packages of goods sent by parcel post on the other. * * * * * The general basis of postal rates is naturally affected in some degree by the fact that the Post Office is a State undertaking, and the propriety of Government control deserves consideration. Adam Smith, with his individualistic leaning, was bound to touch on the question of a State Post Office. He thought there was no objection to the conduct of the Post Office by the Government,[659] and economists since his day have generally followed his view.[660] This acceptance of State control as theoretically justifiable has probably been induced by the logic of facts rather than by the recognition of any peculiar characteristics tending to that view discoverable in the postal service as an industrial organization.[661]